Disentangling excited state behavior of organic exciton-polaritons

Abstract

Exciton-polaritons have emerged as a promising platform for manipulating molecular excited state processes via strong light-matter hybridization, offering new opportunities in nanophotonics and quantum photochemistry. Despite this potential, obtaining a clear picture of polariton dynamics and their associated excited state fingerprints remains highly challenging. The mechanistic interpretation of photophysical pathways under strong coupling has remained ambiguous and at times contradictory. Here, we introduce a systematic strategy to disentangle and identify the spectroscopic features of photoexcited polaritons by jointly tuning the optical cavity architecture and the excitation parameters. Using phase-matched excitation conditions, we monitor coherent relaxation of polaritons with sub-100fs temporal resolution, uncovering an ultrafast decay channel that bypasses the manifold of intracavity dark states. These findings establish practical design principles for controlling coherent light-matter interactions at the nanoscale and challenge the conventional picture of polariton photophysics that emphasizes entropy driven relaxation into dark state reservoirs.